This invention relates to a process for the partial or complete combustion of carbon-containing fuel with an oxygen-containing gas in a reactor under high pressures and temperatures in which the gas formed is removed at the top of the reactor and slag is removed at the bottom of the reactor. The invention also relates to a reactor for use in the process or to other processes wherein a liquid material with solidifying propensity is discharged from a bottom orifice.
Since the carbon-containing fuel is usually of mineral origin, it invariably also contains, in addition to carbon and hydrogen, a certain quantity of inorganic incombustible material, often referred to by the term "ash," which is separated during the complete or partial combustion of the mineral fuel. The residual ash collects as a molten slag and iron in the hearth of the reactor from which it is discharged (commonly known as slag-tapping) downwardly through a slag tap outlet or orifice in the hearth into water contained in a quenching chamber, or water bath, therebelow. The waste slag is then removed from the water bath by conventional means.
Various types of coal contain characteristically different quantities of residual ash and therefore produce different amounts of molten slag. Also, the rheology of the slag may differ from type to type. A slag tap of a fixed size for a particular coal, producing a characteristic quantity of slag of characteristic rheology, may be too small to accommodate another coal having a larger residual ash content and therefore producing a larger quantity of slag or a slag having different rheological characteristics. The larger quantity of slag could block the slag tap orifice and prevent satisfactory slag tapping operation. Thus, the type of coal gasified in the reactor is limited, in part, by the size of the slag tap orifice.
The art is therefore replete with attempts to prevent the accumulation of slag and blockage of the slag tap. For example, Assignee's U.S. Pat. No. 4,834,778 is directed to a method and apparatus for determining the onset of slag tap blockage, and copending application Ser. No. 114,979 filed Oct. 30, 1987 is directed to an interchangeable slag tap, the size of which can be easily changed for differing types of fuel. Assignee's U.S. Pat. No. 4,520,737 is directed to a slag tap cleaner whereby the slag tap may be cleaned (i.e., reamed) without interrupting the combustion process. U.S. Pat. No. 4,680,035 assigned to Combustion Engineering discloses a two-stage slagging gasifier which minimizes back-mixing of reductor gas into the combustor. U.S. Pat. No. 4,479,809 to Texaco is directed to a swirling flow slag trap. Dow Chemical patent 4,653,677 is directed to a slag tap outlet. British Gas patents 4,192,654, 4,129,422, 4,177,042, 4,195,978, 4,126,427 and 4,119,411 are directed to various slag tap designs, including removable hearths. U.S. Pat. No. 4,300,913, of Russian origin, is directed to a double-walled discharge tube. All of these systems, and all others known to Applicant, have one feature in common, i.e., a slag tap centrally located in the reactor. They also have one problem in common, i.e., potential blockage of the slag tap.
The present invention is directed to overcoming this and other related problems in the prior art.
Applicant is not aware of any prior art which, in his judgment as a person skilled in this particular art, would anticipate or render obvious the present invention. However, for the purposes of fully developing the background of the invention and establishing the state of requisite art, the art noted above is set forth.